The present invention relates to a damper disc assembly, particularly to a damper disc assembly having a plurality of friction members inducing hysteresis torque.
The damper disc assembly is employed in the clutch disc assembly of a clutch located between an automobile engine and transmission. Such a damper disc generally is composed of a flanged hub connectable to the transmission main drive shaft, an input rotation member such as a clutch plate and a retaining plate, and elastic members such as coil springs making circumferentially elastic connection of the input rotation member with the hub flange, and friction members such as friction discs sandwiched between the input rotation member and the hub flange.
Torsional vibration twists the input rotation member relative to the hub, and is transmitted from the input rotation member to the elastic members. The elastic members thus deform and the friction members counterslide, effecting torsional vibration damping. Therein, with regard to the torsional characteristics (torsional angle versus torque response) of the damper disc assembly, hysteresis torque is induced depending on the characteristics of the friction members. Generally, the torsional characteristics in operation are such that the hysteresis torque response through the extent of a phase of positive torsioning and that through the extent of a phase of negative torsioning are the same. In defining the torsional characteristics, positive torsioning phase refers to a twisted condition of the input rotation member relative to the hub in the engine rotation direction, and negative torsioning phase refers to a twisted condition of the input rotation member relative to the hub in the direction opposite engine rotation.
However, certain conditions under which an automobile is used therein call for assembly torsional characteristics wherein different hysteresis torque responses to positive versus negative torsioning phases are effected.
One damper disc assembly has been proposed having an wedge-like member interposed between a pressing member and a friction member. The wedge-like member is of varying sectional thickness and gives rise to reduced hysteresis torque response when the damper disc assembly reacts through the extent of a negative torsioning phase. However, this damper disc assembly requires such strict dimensional control of components in order to stabilize hysteresis torque response that it is impractical to achieve desired hysteresis torque characteristics.